#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
#define STACK_MAX_SIZE 100
#define bool int
typedef struct stack {
    int * base;
    int * top;
    int number_of_elements;
} * Stack;
int init_stack(Stack * s);
int push(Stack s, char operator_or_operand);
int pop(Stack s, char * p_operator_or_operand);
int get_top(Stack s, char * symbol);
bool is_operator(char symbol);
bool is_operand(char symbol);
int evaluate(char * expression, int * result);